At the company’s Starbase R&D center in Boca Chica, Texas, SpaceX rocket’s two pieces – an upper-stage named Starship and a booster called Super Heavy – were attached. The spacecraft stands 120 meters (400 feet) tall, dwarfing any prior launch system. It will produce roughly twice the thrust of the vehicles that launched men to the moon when it finally lifts off. The main engines of Apollo’s iconic Saturn V rockets launched at a force of 35 meganewtons (almost 8 million pounds). The new SpaceX Super Heavy booster should be capable of producing roughly 70 meganewtons of thrust. To connect the two segments, a large crane was required. They were kept in place for an hour before being separated again.

To prepare for the debut launch, SpaceX still has weeks or months of testing ahead of it. The booster will launch the Starship into space for a once-around-the-Earth journey, culminating in a “landing” in the Pacific waters near the Hawaiian islands. The Super Heavy will then be sunk in the Gulf of Mexico. NASA, the US space agency, has already hired SpaceX to build a version of the Starship upper-stage that will be able to land men near the lunar south pole this decade. However, SpaceX eventually intends both segments of future spacecraft to make controlled landings, either on land or on sea platforms, so they may be reused. Elon Musk, the company’s CEO, claims that if completely built, the Starship system will be capable of transporting humans to the moon and Mars.